As the use of the Internet and the World Wide Web (“Web”) has become widespread, it is increasingly common for users to access and use various types of capabilities provided by remote computing systems over the Web, including to search for, shop for and order items (such as products, services and/or information) that are for purchase, rent, lease, license, trade, evaluation, sampling, subscription to, etc. In addition to such user-initiated interactions, software programs on remote computing systems may also interact for various purposes and in various ways. For example, there is growing use of the Web to provide so-called “Web services,” which typically involve the programmatic interaction of remote applications to exchange information via defined APIs (“application program interfaces”). Web services allow heterogeneous applications and computers to interact, and may be defined and implemented using a variety of underlying protocols and techniques. For example, some Web service implementations return data in XML (“eXtensible Markup Language”) format using HTTP (“HyperText Transport Protocol”) in response to a Web service invocation request specified as a URI (“Uniform Resource Identifier”), such as a URL (“Uniform Resource Locator”) that includes a specified operation and one or more query parameters. Such URI-based invocation requests may, for example, be based on the use of XML over HTTP (e.g., as part of the REpresentational State Transfer, or “REST”, distributed interaction model that focuses on resources). In other implementations, additional underlying protocols are used for various purposes, such as SOAP (“Simple Object Access Protocol”) for standard message exchange, WSDL (“Web Services Description Language”) for description of service invocations, and UDDI (“Universal Description, Discovery, and Integration service”) for discovery of available services. The use of Web services to enable software programs to interact is in some situations referred to as one example of a service-oriented architecture.
In addition to the use of Web services, various other types of programmatic interaction mechanisms are known in which multiple software programs interact in order to achieve a goal. For example, remote procedure call (“RPC”) protocols have long existed that allow a program on one computer to cause a program on another computer to be executed, and various object-oriented and other architectures such as CORBA (“Common Object Request Broker Architecture”), Java RMI (“Remote Method Invocation”), JavaSpaces, Jini, JXTA, UPnP (“Universal Plug and Play”), and DCOM (“Distributed Component Object Model”) provide similar capabilities. In addition, a variety of middleware programs have been implemented to connect separate applications (often of distinct types and from unrelated sources) to allow communication. For example, various EDI (“Electronic Data Interchange”) networks exist that provide standard mechanisms to allow a computer system of one user of the network to send data to a computer system of another user of the network.
While the use of remote software services by software programs provides various benefits, various problems also exist. For example, each remote service will typically provide its own mechanism for others to access the remote service, such that a software program using multiple remote services may need to manage and support various different access mechanisms (e.g., synchronous method invocation for a first remote service and asynchronous message passing for a second remote service, use of different communication protocols or technologies for different remote services, etc.), which increases the complexity of creating and maintaining the software program. In addition, debugging and other testing of software programs that use remote services may be difficult, as problems that arise during testing may be due to problems in interactions with the remote services (e.g., due to intermittent network problems).